The fuel supply apparatus for the internal combustion engine to be mounted on an automotive vehicle, comprises a fuel tank for reserving the fuel, a fuel pump for pumping up the fuel from the fuel tank to supply the fuel to injectors, and a fluid pressure regulation apparatus such as a pressure regulator and the like for adjusting the fuel supply pressure (hereinafter simply referred to as “fuel pressure”) when the fuel is supplied to the fuel consumption unit by the fuel pump. The fluid pressure regulation apparatus is adapted to adjust the fuel supply pressure to injectors forming part of the fuel consumption unit with the fuel pump for pumping up the fuel from the fuel tank. The fluid pressure regulation apparatus of this kind is generally provided with a housing, and a diaphragm provided in the housing to separate the housing into two chambers and has an adjustment valve at the central portion thereof. The diaphragm has one surface side receiving the fuel pressure in one of the adjustment chambers to have the central portion deformed in the directions to close or open the adjustment valve in response to the fuel pressure varied in the adjustment chamber, and has the other surface side held in engagement with a spring (compression coil spring) to have the diaphragm suppressed from being deformed. The fluid pressure regulation apparatus thus constructed is adapted to have the pressure adjustment valve held in the closed state until the fuel pressure in the pressure adjustment chamber reaches the set pressure. Further, the fluid pressure regulation apparatus is usually disposed in the fuel tank together with the fuel pump.
As a fluid pressure regulation apparatus of this kind, for example, is known a pressure regulator which comprises a housing, a diaphragm disposed in the housing to separate the housing into two chambers, a pressure adjustment chamber positioned at the one surface side of the diaphragm and having a fuel introduction port in which the pressurized fuel to be introduced from the fuel pump and a fuel discharge port through which the surplus fuel to be discharged, a back pressure chamber positioned at the other surface side of the diaphragm to allow back pressure fluid to be introduced therein, a plunger slidably disposed in the housing and formed with an open chamber opened to the atmosphere between the diaphragm and the back pressure chamber, a valve portion member attached with the diaphragm to selectively open or close the fuel discharge opening in response to the displacement of the diaphragm, a spring interposed between the diaphragm and the plunger to urge the valve portion member in a direction having the valve portion member closed, and a stopper unit for defining the movement range of the plunger. The fuel supply apparatus provided with the pressure regulator thus constructed is adapted to switch the set loads of the spring into two stages depending on whether or not the back pressure fluid is supplied to the back pressure chamber, thereby making it possible to switch the regulation pressure value between a low pressure value and a high pressure value (for example see Patent Document 1).
Another conventional fluid pressure regulation apparatus, for example, comprises first and second diaphragms separating a housing into three pressure chambers, a valve body attached with the first diaphragm to selectively open or close the pressure regulating discharge port in the first pressure chamber formed between the housing and the first diaphragm, a pressure receiving member connected to the valve body through a connecting rod disposed in the second pressure chamber between the first and second diaphragms and secured to the second diaphragm, and a spring disposed in the third pressure chamber between the housing and the second diaphragm to urge the pressure receiving member in a direction having the valve body closed. The fuel supply apparatus provided with the pressure regulator thus constructed is adapted to control the pressure of the fuel supplied to the second and third pressure chambers, thereby making it possible to switch the fuel pressure to be adjusted into three stages (for example see Patent Document 2).